A calcium aluminum silicate (Ca2Al2SiO7) phosphor doped with different concentrations of cerium has been prepared by a solid-state reaction method. From X-ray diffraction (XRD) data and using the Rietveld refinement method, the phase, structure, and average crystalline size have been determined. Luminescence emissions have been investigated by optically stimulated luminescence (OSL) and thermoluminescence (TL) methods. TL studies reveal a broad peak centered at 220 °C with an emission band at 410 nm. The TL intensity of a sample doped with 0.1 mol% Ce proved to be 115 times stronger than that of an undoped sample. Electron paramagnetic resonance (EPR) has been utilized to detect the defect centers responsible for the TL process in Ce-doped Ca2Al2SiO7 phosphor. The observed EPR spectrum results from a superposition of three defect centers. Center I with a g-value of 2.0090 is assigned to an O− ion and exhibits hyperfine interaction with a nearby nucleus with spin 3/2. This center relates to the TL peak at 220 °C. Center II with an isotropic g-value of 2.0073 is also ascribed to an O− ion and correlates with the dominant 220 °C TL peak. Center III has a g-value of 2.0076 and is identified as an F+ center (singly-ionized oxygen vacancy).